The radio frequency (RF) spectrum is a limited commodity. Only a small portion of the spectrum can be assigned to each communications industry. The assigned spectrum, therefore, must be used efficiently in order to allow as many frequency users as possible to have access to the spectrum. Multiple access modulation techniques are some of the most efficient techniques for utilizing the RF spectrum. Examples of such modulation techniques include time division multiple access (TDMA), frequency division multiple access (FDMA), and code division multiple access (CDMA).
Whenever possible, wireless service providers enhance the reliability and performance of the wireless networks they operate in order to attract and retain subscribers. One of the key performance parameters of any wireless networks is call set-up. When a new call is initiated by a mobile station (e.g., cell phone) or is directed to a mobile station by a base station, a series of call set-up messages are wirelessly transmitted between a mobile station and a base station of a wireless network. All of these messages must be successfully received by either the base station or mobile station in order for the mobile station to successfully access the wireless network and transmit and receive on a traffic channel. If one of the control messages is not received, either due to noise or an obstruction, a call may be dropped during set-up and must be reinitiated. This wastes bandwidth and ties up system resources.
For example, in a conventional wireless networks, such as a CDMA wireless network operating according to the IS-95 standard or the IS-2000 standard, a single point-to-point Channel Assignment message (CAM) is transmitted in a paging channel from a base station to a mobile station. The CAM comprises a number of data fields that contain information about the assigned channel, such as Walsh code, frame offset, power, CDMA frequency and the like. Due to noise, obstructions or another unforeseen situation, a call may not be completed if the mobile station fails to receive the CAM during a required time period set forth by the applicable standard. If the resulting access failure rate or system failure rate in the forward link is relatively high, the required system performance cannot be guaranteed.
Therefore, there is a need in the art for improved systems and methods for setting up a call between a base station and a mobile station in a wireless network. In particular, there is a need for an improved wireless network that can transmit a Channel Assignment message to a mobile station with a high probability of success.